Process for metal removal from petroleum residues



Sept. 23, 1969 A. DESCHAMPS ET AL 3,468,790

PROCESS FOR METAL REMOVAL FROM PETROLEUM RESIDUES Filed March 11, 1968 Q a I a o e w m s Q i ATTOR NEYS United States Patent 3,468,790 PROCESS FOR METAL REMOVAL FROM PETROLEUM RESIDUES Andr Deschamps, Chatou, and Philippe Renault, Neuillysur-Seine, France, assignors to Institut Francais du- Petrole des Carburants et Lubrifiants, Rueil-Malmaison, Hauts-de-Seine, France Filed Mar. 11, 1968, Ser. No. 712,088 Claims priority, application France, Mar. 9, 1967, 2

US. Cl. 208-251 23 Claims ABSTRACT OF THE DISCLOSURE An object of the process according to this invention is to remove mineral impurities from the crude petroleum and fractions thereof after reduction of the same.

Amongst such impurities, nickel and vanadium, which are used for the most part in the compounds of the porphyrines type, are very troublesome for refiners and users since they are responsible for the poisoning of cracking and hydrodesulphurization catalysts, as well as for corrosion of the apparatus wherein is carried out the combustion of fuels, in particular the turbines working under high temperature conditions.

A number of different processes have been proposed in order to eliminate these organometallic complexes; amongst them are to be mentioned the treatments with acids, with bases, by means of complexing agents, of foaming agents, hydrogenation at high temperature and under high pressure in the presence of a catalyst.

It has also been proposed to extract these complexes by means of such solvents as dirnethylsulfoxide, furfurol or 2-pyrrolidones.

In the processes using a solvent, the metal impurities are dissolved mainly in the solvent. Nevertheless, such processes generally suffer from one or several inconveniences such as:

An insufiicient rate of metal removal;

A substantial loss of the petroleum product;

A relatively high cost, attributable generally to the cost of the solvents.

For example, according to U.S. Patents No. 3,502,627 filed on May 22, 1959, metal porphyrines are extracted by means of Z-pyrrolidone or one of the derivatives thereof.

The petroleum cut is mixed with Z-pyrrolidone and the mixture is decanted. Two phases are separated. The lower layer, consisting of the pyrrolidone containing a part of the metal impurities dissolved therein, together with hydrocarbons of the cut, forms the extract. The higher hydrocarbon layer constitutes the rafiinate.

It is observed that this process is only applicable to petroleum cuts which only contain porphyrines of type I, i.e., according to this patent, to volatile metal-porphyrine complexes. The demetalization (or metal removal from) petroleum cuts which contain heavier porphyrines is therefore not possible.

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Besides, the solvent used is costly. It can be used in smaller amounts, if diluted with a cheap alcohol but the maximal alcohol proportion is 50% and practically comprised between 20 and 25%.

An object of the present invention is, at the opposite of the preceding technique, to extract the major part of the hydrocarbons without carrying along therewith the metal impurities, which are thus concentrated in a fraction which corresponds to only a small percentage of the starting reduced crude petroleum.

The demetalization process, object of this invention, may be carried out according to one of the two following methods:

According to the first method, the petroleum cut to be purified is contacted with a solvent such as hereunder defined in which the hydrocarbon cut is dissolved. Thereafter is added an antisolvent which will be also defined hereinafter; this second liquid causes the separation of the major part of metal impurities which are in the form of solid conglomerates carrying along therewith a small part of the hydrocarbon cut and of the mixture solvent+ antisolvent. The major part of the hydrocarbon cut, substantially free from metals (and other impurities) remains dissolved in the mixture solvents-antisolvent.

As solvent is used a hydrocarbon ether, linear or cyclic, saturated or not, having from 3 to 12 and preferably from 4 to 7 carbon atoms, said solvent containing from 1 to 3 ether functions in the molecule. By way of non-limitative examples are mainly to be mentioned the following solvents; methylethyl-ether, diethylether, ethyl-propylether, dipropylether, ethyl-butylether, vinylbutylether, dibutylether, 1,3-dioxane, 1,4-dioxane, 4,4-dimethyl-1,3-dioxane, 1,3-dioxolane, Z-methyl, 1,3-dioxolane, tetrahydrofuran.

Cyclic saturated ethers and more particularly tetrahydrofuran are preferred.

There are generally used from 0.5 to 8 and preferably from 1 to 4 volumes of solvent per volume of the charge.

The antisolvent is either water or and alcohol or polyol of low molecular weight, i.e. having from 1 to 10 and preferably from 1 to 5 carbon atoms per molecule. As antisolvents are to be mentioned, in a non-limitative Way, ethanol, ethylenegylcol, l-propanol, glycerol, l-butanol, Z-butanol, l-pentanol, l-heptanol. However primary mono-alcohols of low molecular weight will be preferred.

There will be used generally from 0.1 to 2 and preferably from 0.3 to 1 volume of antisolvent per volume of solvent. It must be understood that it is possible, if so desired, to make use of a mixture of solvents and/ or antisolvents such as hereinbefore defined.

It is also quite possible to bring directly into contact a mixture of solvent and antisolvent with the charge sub-' jected to purification, and to operate in situ the mixture of these three compounds (hydrocarbon charge-solventantisolvent) However it is preferred to cause the solvent to act first and thereafter the anti-solvent. This operating manner results in a more rapid and eiiicient operation and does not require a so strong stirring as in the case of simultaneous introduction of the solvent and the antisolvent.

The second method for carrying out the invention, which constitutes the preferred one, consists of contacting the hydrocarbon cut to be purified with a bifunctional organic compound, i.e. a liquid organic compound containing at least one ether function (preferably from 1 to 5) and at least one alcohol function (preferably from 1 to 5), said bifunctional compound having from 3 to 40 carbon atoms and preferably from 4 to 10 carbon atoms and being either linear or cyclic, saturated or not.

By way of non-limitative examples of bifunctional compounds there will be mentioned: ethyleneglycol ethyl monoether, ethyleneglycol propyl or butyl monoethers,

diethyleneglycol, triethyleneglycol and their higher homologs, diethyleneglycol monoethyl ether, glycerol diethyl ethers, 2(hydroxy-methyl) tetra-hydrofuran, dipropyleneglycol, tetrapropyleneglycol.

The bifunctional compound may be used either alone or in admixture with one or more sol-vents and/ or antisolvents as hereabove defined.

There will be used generally from 0.5 to 8 and preferably from 1 to 4 volumes of bifunctional compound per volume of hydrocarbon charge to be purified.

When to the bifunctional compound is associated a solvent or an antisolvent, the latter will be used in an amount of from 0.01 to 0.5 and preferably from 0.05 to 0.2 times the volume of the bifunctional compound.

In case of use of such a bifunctional compound as ethylene glycol butylmonoether or 2-butoxyethanol, it is observed that the petroleum residue is immediately separated in two fractions the first, which is the most important one, mainly contains demetalized petroleum residue; the second essentially contains asphaltenes and the metals which soiled said petroleum residue.

On the contrary, when there is used a couple solventantisolvent, the precipitation of metal impurities only occurs when the petroleum residue, previously dissolved in the solvent, is brought into contact with the antisolvent.

The demetalization treatment according to the two above defined methods, can be applied either to reduced crude oils, i.e. to residues of distillation under a pressure close to the atmospheric pressure or to the products obtained by fractionating these atmospheric residues, for instance to cuts obtained by vacuum distillation of atmospheric residues. There are mainly to be mentioned the hydrocarbon cuts included in the category/of kerosenes, fuels, gas oils, oils. The residue from vacuum distillation may also, if not too viscous, be purified according to the process of this invention. From a general point of view the charge subjected to the treatment of this invention will have an initial boiling point higher than 250 C. under a pressure of 76 cm. of Hg. In the following, for sake of simplicity, there will be used the term of petroleum residue, being understood that this term may involve the above-defined hydrocarbon cuts.

The contact between the petroleum residue and the couple solvent-antisolvent or the bifunctional compound (associated or not to a solvent or antisolvent) may be achieved into a conventional apparatus such as an agitated tank or an extraction column operated with countercurrent. In any case, whatever may be the way of carrying out the invention, the contact temperature may vary Within wide limits, for instance between 20 and 150 C. and preferably between 30 and 80 C.

In a second stage, the two-obtained phases are separated and the solvents recovered therefrom by any conventional means such as distillation, washing with water, distillation with steam.

The fraction which contains the most part of the organo-metallic compounds also contains asphaltenes, resins and is moreover enriched with sulfur and nitrogen compounds.

The process of demetalization object of this invention may therefore be used for deasphalting petroleum residues.

It must be observed that the usual deasphalting processes are not convenient. For instance the process of deasphalting by means of propane, although providing for a partial demetalization, results in a too high loss of petroleum product.

The following non-limitative examples are given for illustrative purposes.

Examples 1 to 6 illustrate the batch operation of the invention, whereas Example 7, on the contrary, illustrates the carrying out of the invention in a continuous manner.

4 Example 1 1 kg. of atmospheric residue from Kuwait crude oil, containing 46 parts per million of parts (p.p.m.) by weight of vanadium and 15 p.p.m. of nickel, is contacted, at ambient temperature, with 3 kg. of tetrahydrofuran and then with 2.65 kg. of ethyl alcohol at a concentration of The metal impurities precipitate after the addition of alcohol. After decantation, separation of the phases, and recovery of solvents by evaporation, there are obtained 0.9 kg. of residue containing only 4 p.p.m. of vanadium and 4 p.p.m. of nickel, which may be used as fuel.

Example 2 Example 1 is repeated with 1 kg. of atmospheric residue from Safaniya crude, containing 78 p.p.m. of vanadium and 28 p.p.m. of nickel. There are used 3 kg. of bifunctional compound consisting of 2-butoxy ethanol. The metal impurities precipitate as soon as the residue is contacted with the bifunctional compound. The following operations are the same as in Example 1. There are obtained 0.76 kg. of a residue containing only 15 p.p.m. of vanadium and 3 p.p.m. of nickel, which can be used as fuel.

Example 3 Example 2 is repeated with 1 kg. of residue from Safaniya crude, containing 78 p.p.m. of vanadium and 28 p.p.m. of nickel (the same as in preceding example), which is contacted, at ambient temperature, with a mixture of 2 kg. of 2-butoxy ethanol with 0.16 kg. of 95% ethyl alcohol. After recovery of the solvents as precedingly, there are obtained 0.8 kg. of a fuel having only a 15 p.p.m. vanadium content and a 3 p.p.m. nickel content.

Example 4 Example 1 is repeated with the same charge (1 kg. of Kuwait atmospheric residue) which is first contacted with 3 kg. of 1-4 dioxane and thereafter with 0.4 kg. of water.

The subsequent operations are the same. There are obtained 0.87 kg. of a residue containing only 6 p.p.m. of vanadium and 5 p.p.m. of nickel.

When the same experiment is repeated by causing 1-4 dioxane and water (in the same proportion) to act simultaneously, substantially the same results are obtained but it is necessary to stir much more vigorously the mixture of the treated residue with the solvents, which results in a lengthening of the operation.

Example 5 By repeating Example 1 with the same charge and under the same conditions btu with the use as solvent of 2 kg. of isopropyl ether, and as antisolvent of 1.5 kg. of 95% ethyl alcohol, there are recovered 0.85 kg. of a fuel containing 8 p.p.m. of vanadium and 4 p.p.m. of nickel.

Example 6 Example 3 is repeated with the same charge and in the same operating conditions but with the use of a mixture of 2 kg. of 2-ethoxy ethanol and 0.3 kg. of tetrahydrofuran, these two compounds being simultaneously brought into contact with the residue.

The following results are obtained:

0.75 kg. of fuel are recovered (yield of 75%) The vanadium and nickel content were respectively of 17 and 5 p.p.m.

Example 7 This example illustrates the complete operation of the process with the use of ethylene glycol n-butyl mono-ether or 2-butoxyethanol in combination with a small amount of water. Due to the particular features of the installation diagrammatically shown in the accompanying drawing,

Ethylene-glycol n-butyl mono-ether 75 Recycled petroleum residue 1O Heptane Water 5 Into the mixer 1 are formed two phases: a heavy phase containing the major part of the metal impurities and the asphaltenes, which is discharged through duct 9, and a lighter phase consisting essentially of demetalized petroleum residue dissolvedin 2-butoxy ethanol, which is conveyed through duct 10 to the separator 2. The separator is also fed with a water stream, introduced through duct 11, and the object of which will be defined hereunder.

In this apparatus takes place the separation between the demetalized petroleum fuel which flows through duct 12 and the 2-butoxy ethanol which is dissolved and carried along with the water stream toward the distillation column 3, through duct 13.

The petroleum fuel is made free from the bifunctional compound still contained therein, by distillation with steam into apparatus 6. There is recovered from duct 14 the demetalized petroleum fuel substantially free from 2- butoxy ethanol and heptane.

From the distillation column 3 are recovered, at the bottom the 2-butoxy ethanol which is recycled through ducts and 8 to the initial mixer 1, and at the top, through duct 16, an 80% water-% 2-butoxy ethanol azeotrope as well as heptane. After passage through a condenser this flow is conveyed to the decanter 5 the object of which will be explained in detail hereafter.

The heavy phase issued from the mixer 1 is subjected into apparatus 4 to a distillation with steam so as to extract 2-butoxy ethanol and heptane, which are both conveyed to the decanter 5 after passage through the condenser. The heavy fraction containing metal impurities and substantially free from 2-butoxy ethanol and heptane, is discharged through duct 18.

The decanter 5 is fed with the outflows from the distillation column and from apparatus 4 and 6 for distillation with steam, i.e. with fluid streams flowing respectively through ducts 16, 17 and 19. These outflows consist of water, ethylene glycol monobutyl ether and heptane.

Into the decanter 5 two phases are separated: an organic phase consisting of 2-butoxy ethanol and heptane, which is recycled to mixer 1 through ducts 20 and 8 and an aqueous phase. This aqueous phase is conveyed partly to the separator 2 through duct 11 and partly to the boiler 7 through duct 21, this boiler supplying with steam the apparatuses 4 and 6 through ducts 22 and 23.

It must be pointed out that the installation diagrammatically shown in the drawing represents the preferred embodiment of the invention. As a matter of fact the demetalization is carried out by means of a bifunctional compound (in the present case ethylene-glycol monobutyl ether) in combination with a small percentage of water. Demetalization itself takes place only into the mixer 1.

It could be possible, if desired, to carry out the distillation into column 3 or to complement this distillation by a dehydration so that the bifunctional compound conveyed through duct 15 be substantially free from water. Similarly the organic liquid conveyed through duct 20 could be dehydrated. The contact would then be made into the mixer 1 between the treated residue and the bifunctional compound in the absence of antisolvent. However these complementary steps are not necessary.

The water introduced into separator 2, only acts, in such case, are extracting agent for 2-butoxy ethanol (and not as antisolvent) since, at this stage, the major part of the metallic impurities have been eliminated.

The heptane also acts, in the decanter 5, as an extracting agent for 2-butoxy ethanol but, this time, contained in the aqueous phase.

The heptane could be replaced by any other saturated hydrocarbon having for example from 5 to 8 carbon atoms, or by a hydrocarbon cut containing two or more of such saturated hydrocarbons.

Of course there could be used other modifications in the step of recovering demetalized fuel, which are however less preferred, such as, for example that according to which said step is carried out by total distillation of the liquid from duct 10.

In a unit such as diagrammatically shown in the drawing there has been treated a reduced crude oil from Safaniya identical to that of Examples 2, 3 and 6. There was recovered, through duct 14, of the treated fuel with only a 5 p.p.m. nickel content and a 16 p.p.m. vanadium content.

What is claimed as this invention is:

1. A process of demetalization of a petroleum fraction consisting essentially of residue of crude petroleum distillation, said residue having a boiling point higher than about 250 C., which comprises contacting the petroleum fraction to be demetalized in the liquid phase with at least one member selected from the group consisting of:

(a) a couple solvent-antisolvent wherein the solvent is an ether containing about 3 to 12 carbon atoms and from 1 to 3 ether functions per molecule and the antisolvent is selected from the group consisting of water, alcohols and polyols containing from about 1 to 10 carbon atoms, and

(b) a bifunctional organic compound containing at least one ether function and at least one alcohol function and containing about 3 to 40 carbon atoms per molecule, and separating the metallic impurities from either the purified petroleum fraction in solution in the mixture of solvent-antisolvent or the abovedefined bi-functional compound.

2. A process according to claim 1 using a couple solvent-antisolvent, wherein the petroleum fraction is first contacted with the solvent and thereafter with the antisolvent.

3. A process according to claim 1 wherein the petroleum fraction is contacted with a bifunctional compound which has been previously admixed with an antisolvent.

4. A process according to claim 1 wherein the petro leum fraction is contacted with a bifunctional compound which has been previously admixed with a solvent.

5. A process according to claim 1 using a couple solvent-antisolvent, wherein the solvent contains about 4 to 7 carbon atoms per molecule and the antisolvent is selected from the group consisting of alcohols and polyols containing about 1 to 5 carbon atoms in the molecule.

6. A process according to claim 1 using functional compound, wherein said compound contains about 4 to 10 carbon atoms per molecule.

7. A process according to claim 1 using a couple solvent-antisolvent, wherein the solvent is a saturated cyclic ether and the antisolvent a primary monoalcohol.

8. A process according to claim 1 using a bifunctional compound, wherein said compound is selected from the group consisting of glycol monoethers.

9. A process according to claim 1, using a couple solvent-antisolvent, wherein about 0.5 to 8 volumes of solvent per volume of the petroleum fraction to be demetalized and about 0.1 to 2 volumes of antisolvent per volume of solvent are utilized.

10. A process according to claim 1, using a bifunctional compound, wherein about 0.5 to 8 volumes of bifunctional compound per volume of the petroleum fraction to be demetalized are utilized.

11. A process according to claim 9 wherein about 1 to 4 volumes of solvent per volume of the petroleum fraction to be demetalized and about 0.3 to 1 volume of antisolvent per volume of solvent are utilized.

12. A process according to claim 10 wherein the bifunctional compound is used in an amount of about 1 to 4 volumes per volume of the petroleum fraction to be demetalized.

13. A process according to claim 1 wherein the Contact is carried out at a temperature of about 20 and 150 C.

14. A process according to claim 1 wherein the solvent is tetrahydrafuran and the antisolvent is ethanol.

15. A process according to claim 1 wherein the bifunctional compound is 2-butoxy ethanol.

16. The process of claim 1, wherein the solvent is selected from the group consisting of methyl ethyl ether, diethyl ether, ethyl propyl ether, dipropyl ether, ethyl butyl ether, vinyl ether, dibutyl ether, isopropyl ether, 1,3-dioxane, 1,4-dioxane, 4,4-dimethyl-1,3-dioxane, 1,3- dioxolane, Z-methyl, 1,3-dioxolane and tetrahydrofuran.

17. The process of claim 7, wherein the solvent is tetra hydrofuran.

18. The process of claim 1, wherein the antisolvent is selected from the group consisting of ethanol, ethylene glycol, l-propanol, glycerol, l-butanol, 2-butan0l, 1- pentanol and l-heptanol.

-- of'the bifunctional compound.

19. The process of claim 1, wherein the bifunctional organic compound is selected from the group consisting of ethylene glycol ethyl monoether, ethylene glycol propyl monoether, ethylene glycol butyl monoether, diethylene glycol, triethylene glycol, diethylene glycolmonoethyl ether, glycerol diethyl ether, 2(hydroXy-methyl) tetrahydrofuran, dipropylene glycol, tetrapropylene glycol, '2- butoxy ethanol, 2-ethoxy ethanol, and higher homologs of said compounds.

20. The process of claim 3, wherein the antisolvent is used in an amount of about'0.01 to 0.5 times the volume 21. The process of claim 3, wherein the solvent is used in an amount of about 0.01 to 0.5 times the volume'of the bifunctional compound. v I

22. The process of claim 1, wherein the content is carried out at a temperature of about 30 to C.

23. The process of claim 1, wherein the metal impurities include nickel and vanadium.

I References Cited UNITED STATES PATENTS 2,761,821 9/1956 Jahnig 19652 DELBERT E. GANTZ, Primary Examiner J. M. NELSON, Assistant Examiner U.S. Cl. X.R. 20888 

